Thermostatic switch



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L. P. HUTT THERMO STATIC SWITCH Filed April 50, 1950 Sept. 29, 1931.

Patented Se t. 29, 1931 STATES PATENT OFFICE LEONARD P. BUTT, OF SCHENECTADY, NEX YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF YORK THERMOSTATIC SWITCH Application filed April 30,

My invention relates to control devices, nore particularly to an automatic switch ?or controlling temperature, speed, pressure and the like.

When high temperatures, speeds and pres- :ures are to be controlled increasing difii- :ulties arise which are not present in conrolling devices for controlling normal lpeeds, pressures, temperatures and the like. It is usually desired to control these speeds, )ressures and temperatures between narrow imits at relatively high values. It will, herefore, be seen that below and above hese predetermined limits the control neans must have no elfect upon thespeeds, )ressures or temperatures which have been :stablished. I

For example, where very high temperttures are encountered as in connection vith cooking grease used in bakeries or in :onnection with the wax used for waxing rperations in the construction of shoes, and 11 similar industries, a switch of this char Lcter must operate between narrow limits Ll? high temperatures and also must be *aised from room temperatures to high vorking temperature without affecting the )roper operation of the controlling means. Bome means, therefore, must be provided 'or preventing operation of the controlling upparatus while the controlling apparatus 3 brought up to the operating temperature.

It has been found that at high'temperttlll'OS the overshooting of control appaatus is more difficult to control than at ower temperatures. It is, therefore, desir- ,ble to provide a means to permit overhooting without damaging the parts of the ontrol device.

Due to thehigh temperature encountered nly small increments of expansion due to, emperature changes can be utilized in operting the controlling means and therefore, ome form of multiplying means must be nserted in the controlling means to provide device which is practical to operate the ontrolling means.

The bellows'type of control means which ro'rmally makes use of gas cannot be used ince gas does not have a straight line func- 1930. Serial No. 448,730.

casional overshooting without damage to the switch part-s.

It is another object of my invention to provide a device which will multiply small increments of expansion sufliciently to operate a switch.

Other objects will appear hereinafter.

In the preferred embodiment of my invention, I provide an automatic switch which responds to the action of a flexible metallic bellows. The temperature responsive medium used to actuatethe bellows is a liquid such as turpentine, for example. A multiplying lever mechanism having lost motion connections to permit overshooting is provided between the bellows and the switch mechanism whereby small increments of expansion of the bellows will actuate the switch mechanism within the operating limits. In my device, a resilient means is biased to open the switch mechanism and a second resilient means actuates the lever mechanism to close the 1 switch mechanism unless the bias is removed from the lever mechanism by means of the bellows. A. novel means is provided for adjusting the fulcrum of one of the levers to thereby vary thetemperature to which the mechanism responds.

My invention will be from the following description when considered in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the accompanying drawings, Fig. 1

illustrates a plan view of my invention with the cover partially broken away to show 1 the interior thereof; Fig.2 is a perspective better understood view of my device with portions thereof removed to show the operating mechanism for the switch.

Referring to the drawings, the bellows 11 is provided with a bulb 11 which is inserted into the medium the temperature of which is to be controlled. Both the bellows and the bulb are filled with some liquid which has a straight line function, that is, a liquid which expands equally for equal increments of temperature changes over very wide limits. The expansion and contraction of the bellows 11 operates through intermediate mechanisms to open and close the contacts 13 and 14 in response to the temperature changes.

The intermediate mechanism consists of a plurality of levers 12 and 20 having a multiplying effect and energizes a snap switch supporting the contacts. The bellows 11 acts directly upon a lever 12 which is pivotally mounted on a slidable support 15. This support 15 may be adjusted to vary the temperatures to which the device responds as will be explained later. A spring 18 enages the lever arm on the opposite side rom the bellows and is biased to close, the switch contacts 13 and 14. The switch mechanism is provided with the lever 20 mounted on the pivot 21 and is connected to the pivoted member 26 also mounted on the pivot 21 by means of the pivoted member 27 and spring 28 for operating the pivoted member 26 to open and close the contacts with a snap action. The pivoted member 26 supports an insulating member to which arm 24 carrying the contact 13 is attached. A spring mounted on the support 23 engages the lever 20 and is biased to open the switch mechanism. It will thus be seen that the spring 22 is opposed to the spring 18, the latter spring overcoming the bias of the spring 22 to close the switch unless the bias of the spring 18 is overcome by the action of bellows 11. A stop 29 is" provided for the contact member 13 to limit movement thereof to the open position.

Referring to the bellows member 11, it is necessary to raise the temperature-responsive medium with which the bellows is filled to the high operating temperatures before causing any operation of the switch mechanism. This is accomplished by providing a space between the bellows member 11 and the lever 12 such that the contact with the lever 12 does not take place until the bellows member has been raised to the operating temperatures. Thus, until the bellows member 11 contacts with the lever 12 and opposes or overcomes the bias of the spring member 18, the spring member 18 will hold the switch member to keep the contacts closed.

The sliding support 15 in which the lever 12 is mounted may be adjusted by loosen- ,ing the member 16 and adjusting the screw member 17. Thus the space between the bellows member and the lever may be changed. By increasing the space between the bellows member and the lever, it will be apparent that before the lever 12 is actuated by the bellows a higher temperature must be reached to produce an expansion of ,the bellows large enough to make contact with the lever to operate the switch mechanism. Conversely, if the space between the lever and the bellows is decreased, lower temperatures will operate the switch mechanism. Fine temperature adjustments are accomplished by adjusting the screw means 19 carried by the lever 12. By adjusting the screw 19 to permit the lever mechanism to move closer to the bellows, lower operating temperatures will result whereas by moving the lever farther away from the bellows, higher temperatures will result.

The operation of the device is as follows. As the medium to be heated increases in temperature, the fluid carried by the bulb 11 responds thereto and expands accordingly, thus expanding the bellows 11 and moving the end of the bellows closer to the lever 12 as the temperature increases. Some predetermined temperature is finally reached where contact is made with the lever 12. As, the temperature increases, the bellows expands and forces the lever 12 about its pivot in a counter-clockwise direction. The screw 19, of course, is moved out of contact with the pivoted lever member 20 and permits the spring 22 to urge the pivoted member 20 about its pivot 21 in a counter-clockwise direction.

As the lever 20 moves in a counter-clockwise direction, the pivoted end of the pivoted member 27 moves to the left until a position is reached where the pivoted member 27 and the spring member 28 are lying in the same plane. The spring is tensioned at this point and as the pivoted end of the pivoted member 27 moves farther to the left, the stored energy in the spring 27 causes the member 26 carrying the contact 13 to pivot about the pivot member 21 in a clockwise direction to open the contacts 13 and 14 with a snap action.

As the temperature decreases, the bellows 11 contacts and permits the spring 18 to again force the screw into contact with the pivoted member 20, thus closing the switch contacts 13 and 14.

The operating temperature scale may be adjusted as set forth above by adjusting the screw 17 to move the slidable member 15 and fine adjustments can be made by adjust ing the member 19.

It will be noted that by having the lever 12 and the lever 20 mounted transversely to each other that very small changes in the length of the bellows will affect comparatively larger movements of the leve r to operate the switch mechanism. This permits the switch mechanism to be made into trated and described herein has been selected for the purpose of clearly setting forth the 20 rinciples involved. It will be apparent, however, that the invention is susceptible of being modified to meet the different conditions encountered in its use and I, therefore, aim to cover by the appended claims all modifications within the true spirit and scope'of my invention.

What I claim as new and desire to secure by Lettprs Patent of the United States is: 39 1. In combination, a movable switch member, oppositely acting biasi-ngmeans therefor, one of said means predominating, and automatic means having a part movable proportionately to variations in a predetermined condition and adjustably connected to render said predominating biasing means elfective and ineffective upon opposite variations of said condition from a different predetermined value. 4G 2. In combination, a movable switch member, oppositely acting biasing means therefor, one. of said means predominating, an automatic means having a part'movable proportionatel to variations in a predetermined condition, said part having a lost motion connection with said predominating biasing means to permit free movement of the said part upon variation in said condition between predetermined limits and to 0} render said predominate biasing means ineffective upon variation of said condition beyon'd one of said limits.

I 3. In combination, a movable switch mem- 55, her biased to one position, a movable memberbiased to engage said switch member to operate the same to another position, and

' automatic means having a part movable proportionately to variations in a predeterminedjcondition and connected to operate 1 the said movable member'out of engagement with said switch member upon variation in said condition above a predetermined value .and to permit movement of said part independently of said movable member upon continued variation in said condition below said predetermined value.' p

4. Anautomatically operated switch, comprising a switch mechanism, a pressure responsive means automatically responsive to predetermined conditions for operatin said switch mechanism upon variation 0 said condition between predetermined limits, and

means providing lost motionconnections be- .tween said switch mechanism and pressure responsive means, permitting said switch to remain in open position upon variation of said conditions above predetermined limits and to remain in closed position upon variation below predetermined limits.

1 5. In combination, a switch biased to open, means predominatingly biased to close said switch, a pressure operated means responsive to predetermined conditions for removing the bias from said biasing means to permit said switch to open upon variation of said conditions between predetermined limits, and lost motion connections between said switch, biasing means and pressure operated means permitting said switch to remain in open position upon variation of said conditions above predetermined limits, and.to remain in closed position upon variation below predetermined limits.

6. A switch comprising a snap-over switch mechanism provided with a lever, a second lever'contactin with said first lever and biased to close said switch mechanism, and a resilient means contacting with said first lever to opensaid switch mechanism when said bias is removed from said second lever. i

7. In combination, a snap-over switch mechanism provided with a movable lever, a resilient means contacting with saidlever and biased to open the switch, 'a second lever contacting with said first lever and biased to close said switch, and a thermostatic means for rendering said second lever inoperative. v

' 8. A thermostatically controlled switch comprising a switch mechanism, a resilient means for openin said switch mechanism, a pivoted lever biased to close said switch mechanism, a temperature'responsive means for removing the bias to open the switch, and an adjustable fulcrum for pivoting said lever whereby the temperature scale of said switch mechanism may be varied.

9. A thermostatically controlled switch mechanism comprising a switch provided wit a movable lever, a resilient means con tact ng with said lever and biased to open said switchfa second lever contacting said first lever and predominatingly biased to close said switch, a thermostatic means for removing the bias from said second lever, and-an adjustable fulcrum for supporting said second lever, adjustable (to vary the temperature scale of said switch mechanism.

10. A thermostatically controlled switch comprising a snap action switch mechanism, a resilient means biased to open said switch mechanism, a lever predominatingly biased to close said switch mechanism, a thermostatic means for removing the bias from said second lever, a fulcrum for adjustably supporting said lever whereby the temperature scale of said switch mechanism may be varied, and adjusting means for said fulcrum.

11. A thermostatically controlled switch comprising a switch mechanism provided with a lever, a resilient means biased to open said switch mechanism, a second lever transversely disposed to said first lever and contacting therewith whereby a multiplying efiect of movement is obtained, resilient,

means engaging said second lever for moving said first lever to close said switch against its biasing means, a thermostatic means for rendering said second resilient means ineffective to permit said switch mechanism to be closed by its biasing means, and adjustable supporting means for said second lever whereby the fulcrum of said second lever may be moved to vary the temperature scale of said switch mechanism.

12. A thermostatically controlled switch comprising a switch mechanism provided with a lever, an extension on said lever, a resilient means engaging said extension and biased to move said lever to open said switch, a second lever adjustably contacting with said first lever and means biasing said second lever to move said first lever to close said switch, and a thermostatic means for rendering said second lever unresponsive to its bias whereby said resilient means can open said switch.

13. A thermostatically controlled switch comprising a switch'mechanism biased to open and provided with a pivoted lever, a second lever pivotally mounted in a plane transverse to the first leverand contacting with said first lever adjacent its pivot for moving said first lever against the bias of said switch mechanism to close said switch 'mechanism, a spring urging said second lever into contact with said first lever to close said switch, and a thermostatic means- 'closing said switch mechanism, a support slidably mounted and providing a fulcrum for said second lever, adjusting means for said support whereby the fulcrum of said 

